Engine Coolant Temperature (ECT) Sensor

On 2.5L and 4.0L, ECT sensor is installed on thermostat housing. On 4.7L, ECT sensor is located on intake manifold, near generator. It provides a variable signal to PCM that is used to calculate injector pulse width and ignition timing. When engine is cold, PCM will operate engine in an open loop cycle, causing slightly richer air/fuel mixture and higher idle speeds. When normal operating temperatures are reached, PCM will operate engine in a closed loop cycle. See MODES OF OPERATION  under FUEL CONTROL under FUEL SYSTEM.